The present invention concerns a novel method for performing Gaussian convolution in a charge transfer device used as an image sensor or as a shift register array containing any signal there Gaussian convolution is desired.
One of the essential steps required in the processing of optical images which are either forxed or transferred into the wells of a charge transfer device, such as a charge-coupled device (CCD), is the accurate detection of the edges of objects in the image. This has been successfully accomplished at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology by a technique called the difference-of-Gaussian (DOG) technique. In this technique, the original image is convolved with each of two properly chosen Gaussian functions and the results are subtracted. The edges of objects with a characteristic size or spacing related to the widths of the Gaussian functions appear as zero values. For a detailed discussion of this technique, reference should be made to a paper on this subject entitled "Theory of Edge Detection" by D. Marr and E. Hildreth, Proc. R. Soc. London B207 (1980), pp 187-217. Present implementations of the DOG algorithm are carried out on digital computers and require extensive hardware and substantial computational times.